You can establish or terminate the READ CACHE or READ and SYSTEM CACHE functions to control the caching of read requests. Read caching is performed on a track basis. When you need data from a volume, a read request is made to the storage control unit The storage control unit reads the data from the volume and sends it back to you. At the same time, a copy of all the data on the track that the storage control unit accesses is saved in cache that resides in the storage control unit. Any subsequent requests that you make for data on the track can be satisfied from the cache. Read performance is improved when the data for your read requests come from the cache.

You can specify that the storage control unit perform this type of read caching on a volume level. Caching can be turned on and off for individual volumes. This feature gives you greater flexibility to manage the volumes that are using the caching resources.